With the ever increasing amount of credit card fraud, it is essential that the authenticity of credit cards be accurately verified. The term “credit card” used in this specification is intended to include any type of credit, debit or charge card, as well as an ID card, a security card, a keycard or the like in which a hologram is provided on the card. In general, credit cards are provided with a hologram for facilitating both visual and machine verification of the credit card. Visual verification of a hologram of a credit card is carried out by visually inspecting the card in white light. By tilting the card relative to the light, the hologram can be viewed from different angles, thus permitting visual verification of the authenticity of the hologram. One method of machine verification requires directing light of different wavelengths at the hologram, and measuring the diffraction of the light. However, it has been found that this method is of limited value, and counterfeit holograms can be prepared relatively simply which provide for diffraction of light of the respective different wavelengths to accurately simulate diffraction of light by an authentic hologram.
There is therefore a need for a method and apparatus for verifying a hologram which overcomes this and other problems of known verification methods and apparatus.